Answer:
The correct answer is B) 18%
Step-by-step explanation:
Note that the vaccine is already and is 80% effective. This means that if the entire population was administered with the vaccine, only 8/10 would gain immunity leaving 2/10 or 0.2 exposed.
If the new vaccine, therefore, is supposed to be 90% effective, it is only pragmatic to administer it against those who do not have immunity which is 0.2 of the existing population.
So to get the percentage that will develop immunity, we have:
0.2 x 0.9 = 0.18 or 18%
Cheers!
Answer:

Step-by-step explanation:

Subtract what is to the right of the equal sign form both side of the equation but any way the answer is 0
No regrouping: 4.34 + 4.35
Regrouping (carrying): 4.93 + 3.76
Inverse operation is an operation that undoes what was done by the previous operation. Take this simple addition problem 5+2=7. If we want to reverse the addition, we just subtract 7-2=5 and we are back where we started. You do the same for multiplication and division.